This invention relates to a process for the dehydration of a product based on fats which is to be rehydrated.
More particularly, the present invention relates to a process for the dehydration of a food product based on fats which is to be rehydrated, wherein the product is exposed to microwaves under reduced pressure.
Processes for dehydrating food products by microwaves under reduced pressure are known to be the cause of electrical arcing inside the microwave apparatus which, on the one hand, adversely affects the installation and, on the other hand, denatures the product to be treated.
According to UK Patent Application GB No. 2 209 265 A, for example, these problems can be solved by a process in which the food product to be dehydrated is placed in an oil bath inside an enclosure where a reduced pressure of 2660 Pa prevails, the product being subjected to treatment with microwaves.
In this patent, which describes numerous examples in which the food product to be treated consists of apples, it is also pointed out that many other food products, for example cheeses, can be dehydrated.
Now, it has been found that, if it is desired to obtain a dehydrated fat by this process, there is a double diffusion, of oil into the fats to be treated, on the one hand, and of certain fractions of the fats into the oil, on the other hand.
Thus, although a dehydrated fat is effectively obtained by this process, the end product obtained is excessively denatured in relation to the original product and cannot be subsequently used in culinary products.
Accordingly, were carried out tests to determine whether products based on fats could be dehydrated in microwave installations without using an oil bath.
These tests revealed numerous problems.
More particularly, when the fat is treated in the form of pieces a few millimeters thick, as for example in the case of grated cheese, it flows with difficulty which complicates the dosing operations to an extent which is greater, the smaller the size of the pieces. It was thus found that this phenomenon becomes particularly crucial for pieces of which the largest size is under two millmeters, in which case the fats tend to solidify, thus preventing satisfactory flow.
In addition, during dehydration by microwaves, the fats tend to melt which results in heavy exudation from the product to be treated, most of the molten fats then being reabsorbed by the product during cooling.
Thus, during extraction of the final dehydrated product, the constituent pieces are agglomerated so that the product has to be ground in an additional step.
Now, to prevent the fats from remelting during grinding, grinding has to be carried out at a very low temperature under liquid nitrogen. Grinding is thus very difficult to carry out.